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Efficacy of Do-It-Yourself Whitening
as Compared to Conventional Tooth
Whitening Modalities: An In Vitro
Study
SR Kwon M Meharry U Oyoyo
YLi
Clinical Relevance
Professionally applied in-office whitening, professionally dispensed patient-applied home
whitening, and the use of an over-the-counter product are effective in changing tooth color
toward a lighter shade, whereas do-it-yourself whitening is not an effective tooth whitening
modality.
SUMMARY
Aim: To evaluate the efficacy of do-it-yourself
(DIY) whitening as compared to conventional
tooth whitening modalities using different
shade assessment tools.
Methods and Materials: Extracted human mo-
lars (120) were randomly distributed to six
groups (n=20). Whitening was performed ac-
cording to manufacturer’s directions for over-
the-counter, dentist-dispensed for home use,
and in-office whitening. DIY whitening con-
sisted of a strawberry and baking soda mix.
Additionally, negative and positive controls
were used. Two evaluators used the Vita Clas-
sical (VC) and Vita Bleachedguide 3D-Master
with interpolated numbers (BGi) for visual
assessment at baseline and one-week, one-
month, and three-month postwhitening. In-
strumental measurements were performed
with a spectrophotometer. Kruskal-Wallis pro-
cedure was used to assess color changes among
groups and intraclass correlation (ICC) to
evaluate agreement between evaluators.
Results: DIY exhibited lower color change
(DSGU
VC
,DSGU
BGi
,DE*, where SGU =shade
guide unit and E =overall color change)
compared to other whitening groups at all
time points (p,0.05). ICC demonstrated very
*So Ran Kwon, DDS, MS, PhD, MS, associate professor,
Department of Operative Dentistry, University of Iowa
College of Dentistry, Iowa City, IA, USA
Michael Meharry, DDS, MS, associate professor, Midwestern
University Dental Institute, Glendale AZ, USA
Udochukwu Oyoyo, MPH, assistant professor, Dental Educa-
tion Services, Loma Linda University School of Dentistry,
Loma Linda CA, USA
Yiming Li, DDS, MSD, PhD, professor and director, Center for
Dental Research, Loma Linda University School of Dentistry,
Loma Linda CA, USA
*Corresponding author: Department of Operative Dentist-
ry, University of Iowa College of Dentistry, 801 Newton
Rd, #45, S235 DSB, Iowa City, IA 52242-1001, USA; e-mail:
soran-kwon@uiowa.edu
DOI: 10.2341/13-333-LR
Ó
Operative Dentistry, 2015, 40-1, 000-000
good agreement between evaluators with VC
and BGi at each time point. Both shade guides
were related with each other and strongly
related to instrumental measurements
(p,0.05).
Conclusions: DIY whitening was the least ef-
fective whitening modality. Both VC and BGi
are related with each other and have good
correlation with instrumental measurements.
INTRODUCTION
Demand for tooth whitening has been building and
growing for more than a decade as people envision
and desire a ‘‘Hollywood smile.’’ Tooth whitening
now represents the most common elective dental
procedure
1
and has proven to be safe and effective
when supervised by a dentist.
2
More than 1 million
Americans whiten their teeth annually, driving
nearly $600 million in revenues for dental offices.
1
The high demand is also reflected by the wide range
of whitening modalities available: professionally
applied in-office whitening; professionally dispensed
patient-applied home whitening, and over-the-coun-
ter (OTC) products.
2
The penchant to do it yourself has swept through
myriad websites promoting the use of at-home
whitening remedies,
3
including rubbing crushed
strawberries or apples on the teeth. Thus, a new
category has emerged that can be described as do-it-
yourself (DIY) whitening using natural ingredients.
4
The advocated use of fruits such as strawberries and
apples is based solely on anecdotal evidence with the
rationale that they contain malic acid. Considering
the current evidence of the erosion potential of fruit-
containing beverages and smoothies
5-8
and contro-
versies on the safety of DIY methods,
9
appropriate
cautions for their use in tooth whitening is para-
mount.
Tooth whitening efficacy has been evaluated
visually with clinically accepted shade guides and
instrumentally with electronic color measuring
devices. The Vita Classical (VC; Vita Zahnfabrik,
Bad Sa
¨ckingen, Germany) developed in 1956 is one
of the most commonly used shade guides. However,
its use in monitoring tooth whitening has been
disputed due to a lack of logical order, uniform color
distribution, and light shade tabs, thus limiting the
design of whitening studies.
10
The Vita Bleached-
guide 3D-Master (BG; Vita Zahnfabrik) was intro-
duced in 2007 to increase the reliability and
validity of visual color assessments by including
more whitening shade tabs, uniform distribution
between the tabs, and a visually perceivable light
to dark value order.
11
The BG tabs are now
available with new markings, with each tab
marked with odd numbers from 1 to 29 and with
‘‘interpolated’’ even numbers in between. The main
advantage of the interpolated BG (BGi) that has
been reported is that the distribution of the tabs
better corresponds to the American Dental Associ-
ation (ADA) equation that 1 ccu =1SGU=1DE*
(ccu =color change unit; SGU shade guide unit;
DE* =overall color change).
12
With heightened consumer interest in whiter
teeth, it is the responsibility of the dental profession
to educate the patient and the public about the
efficacy and adverse effects of different tooth
whitening modalities, suggest or provide appropriate
whitening options based on patient’s needs and
preference, and establish reliable and valid monitor-
ing tools for the whitening process. According to the
current literature, there seems to be a lack in
knowledge of comparing whitening efficacy of all
four whitening modalities. There is also a lack of
information on the correlation of the newly intro-
duced interpolated shade guide with conventional
shade guides.
The purpose of this study is to compare the efficacy
of DIY whitening as compared to conventional
whitening modalities with respect to tooth color
change. Tooth color change was monitored with
three different shade evaluation methods: visual
assessment using VC and Interpolated BGi and
spectrophotometric color assessment with the Vita
Easyshade Compact (ES; Vita Zahnfabrik).
The null hypotheses to be tested were the
following. First, there will be no difference in tooth
color change among the four different whitening
modalities. Second, there will be no differences in
agreement between the two evaluators using VC and
BGi. Third, there will be no correlation between
visual and instrumental color measurements.
METHODS AND MATERIALS
Sample Selection and Preparation
Extracted sound human third molars without iden-
tifiers (120) were collected and stored in 0.2% sodium
azide solution at 48C. Teeth were cleaned of gross
debris and placed in artificial saliva for 24 hours at
378C prior to initiating the experiment. Artificial
saliva was prepared and replaced daily according to
the modified Fusayama solution as described in
ANSI/ADA Specification 41.
13
2Operative Dentistry
Experimental Groups
Specimens were randomly distributed into six
groups of 20 specimens each and mounted on acrylic
molds to expose the crown portion for the different
whitening treatments. The active ingredient, pH,
and application regimen by group are summarized in
Table 1. The treatment regimen for each group
followed manufacturers’ instructions or recommen-
dations for typical use. DIY represented a method
using a puree of strawberry (15 g) mixed with baking
soda (2.5 g; Arm & Hammer Baking Soda, Church &
Dwight Co, Inc, Princeton, NJ, USA) for five minutes
followed by brushing with a soft toothbrush (Colgate
Oral Pharmaceuticals, Inc, New York, NY, USA) for
30 seconds. The procedure was repeated two more
times at five-day intervals. Group OTC received
daily applications of whitening strips for two hours
(Crest 3D Intensive, Crest Pro Health, Procter &
Gamble, Cincinnati, OH, USA) for seven days. Group
HW was treated with a 10% carbamide peroxide gel
(Opalescence PF, Ultradent Products Inc, South
Jordan, UT, USA) placed in a custom fabricated tray
for six hours for 14 days (0.12 ml/tooth). Group OW
represented the professionally applied group treated
with 25% hydrogen peroxide (Philips Zoom White
Speed, Philips Oral Healthcare, Los Angeles, CA,
USA) with three applications for 45 minutes using
light activation. The whitening material was replen-
ished every 15 minutes according to the manufac-
turer’s instructions. The negative (NC) and positive
control (PC) groups were treated according to the
International Organization for Standardization
(ISO) 28399 protocol with grade 3 water and 1.0%
citric acid for 60 minutes at 358C, respectively.
14
Tooth Color Change Assessment
Two shade guides, the VC and BGi, were used for
visual color assessment (Figures 1 and 2). Measure-
ments were performed under a color-controlled light
box (MM 4e GTI Mini Matcher, GTI Graphic
Technology, Inc, Newburgh, NY, USA) at CIE D
65
,
a color temperature of 6500 K, and light intensity of
’1200 lux by two evaluators with superior color
matching competency (ISO/TR 28642).
15
Results
were expressed in difference of shade guide units
(DSGU) for the respective shade guides. Instrumen-
tal color measurements were performed on the
middle third of the buccal surface using a contact-
type intraoral spectrophotometer (ES), Vita Easy-
shade Compact, with the use of a custom-fabricated
clear jig for repeatable measurements (Figure 3).
The overall color change as measured with the
Table 1: Active Ingredient, pH, and Application Regimen by Group
Group Concentration pH Application Regimen
NC: water of grade 3 7.0 One application (60 min), at 358C
DIY: strawberry mix CA 7.2 Three applications (5 min each) at 5-d intervals
OTC: Crest 3D Intensive 9.5% HP 6.0 One daily application (2 h) for 7 d
HW: Opalescence PF 10% CP 7.4 One daily application (6 h) for 14 d
OW: Zoom WhiteSpeed 25% HP 7.2 Three applications (45 min each) at 5-d intervals
PC: citric acid 1.0% CA 3.9 One application (60 min), at 358C
Abbreviations: CA, citric acid; CP, carbamide peroxide; DIY, do-it-yourself; HP, hydrogen peroxide, HW, home whitening; NC, negative control; OTC, over-the-counter;
OW, office whitening; PC, positive control.
Figure 1. Value-oriented Vita Clas-
sical Shade Guide.
Kwon & Others: 3
spectrophotometer was expressed as DE* from the
Commission Internationale de l’Eclairage. The fol-
lowing equation was used:
DE¼½ðL2L1Þ2þða2a1Þ2þðb2b1Þ21=2
The color differences were calculated relative to
baseline color parameters (L*
1
,a*
1
,b*
1
). Measure-
ments were performed with the VC, BGi, and ES at
baseline (T
1
), one-week postwhitening (T
2
) and one-
month (T
3
), and three-month postwhitening (T
4
).
Statistical Analysis
Measurements of color change included DSGU
VC
,
DSGU
BGi
, and DE*. The Kruskal-Wallis procedure
was used to determine significant differences in color
change among the groups. Friedman’s test was used
to evaluate differences in color change across the
different time points. Intraclass correlation (ICC)
was used to assess the agreement between the two
evaluators using the VC and BGi. Correlations
between visual and instrumental measurements
were assessed with Pearson correlations. Tests of
hypotheses were two sided with an alpha level of
0.05. Analysis was conducted with SAS version 9.2
(SAS Institute, Cary, NC, USA).
RESULTS
Visual and instrumental color changes by groups at
threetimepointsaresummarizedinTable2.
Baseline color parameters of the six groups were
not different with the visual and the instrumental
methods (p.0.05). However, color changes among
the groups were significantly different at all time
periods for the visual and instrumental methods
(p,0.05). Post hoc tests (Scheffe) for VC, BGi, and
ES at one week (T2-T1), one month (T3-T1), and
three months (T4-T1) showed that there were
significantly greater color changes in groups OTC,
HW, and OW than in groups NC, DIY, and PC.
(p,0.05). At three months, the greatest overall color
change (DE*) was observed for group OW (p,0.05;
Figure 4). However, visual assessment showed no
difference among OTC, HW, and OW at three-month
Figure 2. Vita Bleachedguide 3D-
Master with interpolated numbers.
Figure 3. Vita Easyshade Compact
and the use of custom-fabricated
clear jigs for repeated measurements.
4Operative Dentistry
evaluation (p.0.05). At three months, NC, DIY, and
PC showed an overall color change of 2.3, 2.4, and
2.53, respectively, which is less than the percepti-
bility threshold of DE 2.6 units.
16
The levels of ICC demonstrated high agreement
between the two evaluators using both the VC and
the BGi. It is noteworthy that the agreement at
baseline (T1) was significantly lower than the
agreement observed at T2-T4 for both BGi and VC
(Table 3). Assuming linear correlation, the shade
guides were strongly and positively related with
each other. Both shade guides were strongly related
with the instrumental measurements (Table 4).
DISCUSSION
This is the first study that compared the efficacy of a
DIY whitening regimen as compared to three
conventional whitening modalities. The result of
this study is partially limited by the use of extracted
human teeth, which will inherently differ from vital
teeth in the oral environment. Based on the results,
the first null hypothesis was rejected, as significant
differences in color change were detected among the
four whitening modalities. The second hypothesis
was retained; there was no significant difference in
agreement between the two evaluators when com-
paring both shade guides. The data support the
rejection of the third hypothesis because of strong
correlations between the shade guides and the
instrumental measurements.
Several studies have compared the efficacy of OTC
products, home whitening, and in-office whiten-
ing.
17-19
According to a clinical study that compared
three different whitening techniques with respect to
the whitening times required to achieve a defined
level of whitening, the cycles required increased
from office whitening to home whitening to OTC
products. That is, one in-office session was compa-
rable to approximately seven days of home whiten-
ing and 16 days of using an OTC product.
18
Another
clinical study found that home whitening and in-
office whitening were superior to OTC whitening
Table 2: Visual and Instrumental Color Changes (Mean [SD]) by Groups at Three Time Points
a
Group 1 wk (T2-T1) 1 mt (T3-T1) 3 mt (T4-T1)
DSGU
VC
DSGU
BGi
DE* DSGU
VC
DSGU
BGi
DE* DSGU
VC
DSGU
BGi
DE*
NC 0.4(0.8) A0.6 (1.5) AC 3.2 (2.0) A1.3 (1.4) A0.7 (1.8) A2.2 (1.5) AC 1.4 (1.3) A0.1 (1.5) A2.3 (1.0) A
DIY 0.5 (1.1) A1.0 (1.2) A4.0 (1.9) A0.1 (1.8) AC 1.1 (1.4) A4.9 (1.9) AD 0.1 (1.3) A1.0 (2.3) A2.4 (1.4) A
OTC 7.4 (2.4) B11.0 (2.2) B10.0 (2.6) C8.1 (2.0) B11.5 (2.5) B14.6 (2.8) B8.6 (2.3) B12.0 (2.1) B14.0 (3.0) B
HW 7.7 (3.0) B11.6 (2.3) B13.8 (2.4) D7.7 (3.0) B11.4 (2.4) B15.7 (2.8) B7.5 (3.0) B12.0 (2.0) B15.3 (2.4) B
OW 7.7 (1.9) B12.7 (2.0) B17.3 (3.3) E8.0 (2.0) B13.5 (1.9) B18.1 (3.4) B8.0 (2.0) B13.6 (2.1) B17.6 (2.8) C
PC 1.1 (1.2) A1.6 (2.5) AD 5.1 (2.4) A2.0 (1.4) AD 1.7 (1.9) A4.6 (2.1) A1.4 (1.8) A1.4 (2.0) A2.53 (1.0) A
Abbreviations: DIY, do-it-yourself; HW, home whitening; NC, negative control; OTC, over-the-counter; OW; office whitening; PC, positive control.
a
Within columns, different letters indicate means that are statistically different (p,0.05).
Figure 4. Overall color change (DE*)
by group at different time points.
Kwon & Others: 5
products when followed up for up to three months.
19
Our study results showed that the whitening efficacy
of Crest Whitestrips, an OTC product, was compa-
rable to professionally dispensed home whitening
and professionally applied in-office whitening for up
to three months postwhitening when evaluated
visually with shade guides. The varying results
compared to previous studies may be explained by
the difference in study design (e.g., in vivo vs in
vitro) and the difference in whitening products
employed. It is important to point out that the
change from original Whitestrips using a polymer-
based hydrogel system to the new advanced seal
technology with an improved seal and increased
hydrogen peroxide concentrations may have affected
the study results.
20
DIY whitening with strawberries as well as the
positive control group using 1.0% citric acid was not
effective in whitening, which showed that color
change is not due to the acid component in fruits.
Agreement between the two evaluators was very
good for both shade guides VC and the BGi. This is
contrary to a study that showed superior perfor-
mance assessment with the Linearguide 3D-Master
compared to the Vita Classical.
21
This can be partly
explained by the limitation of the lack of lighter
shade tabs in the VC. After specimens were
bleached, the only choice was the B1 tab, resulting
in high agreement between the two evaluators using
the VC. Thus, it is noteworthy to point out that ICC
was higher for BGi than VC at all time points,
although it was not statistically significant.
The results of this study demonstrated a good
correlation between the two shade guides and the
instrumental measurements. This supports the use
of both shade guides as acceptable tooth shade
guides and the use of electronic color measuring
instruments for laboratory assessment of tooth
whitening efficacy, as described in ADA acceptance
guidelines and ISO Standards.
14,22,23
It also suggests
that, whenever possible, both visual and instrumen-
tal methods should be used, as they complement
each other.
24
Within the limitations of the study, the data
provided important information about the efficacy
of different whitening modalities. This will provide a
resource to recommend and educate the public about
the most effective tooth whitening modality. Future
studies on the adverse effects of different whitening
modalities should be performed to address the effect
on surface roughness, microhardness, and surface
morphology. Thus, any abuse of tooth whitening that
may lead to moderate to severe loss of tooth
structure may be prevented.
CONCLUSIONS
DIY whitening with the use of a strawberry
mixture is not an effective tooth whitening modal-
ity when compared to professionally applied in-
office whitening, professionally dispensed patient-
applied home whitening, and an OTC product. Both
shade guides VC and BGi are related with each
other and have good correlation with instrumental
measurements.
Conflict of Interest
The authors have no proprietary, financial, or other personal
interest of any nature or kind in any product, service, and/or
company that is presented in this article.
(Accepted 26 May 2014)
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Table 3: Agreement Between the Two Evaluators Using
VC and BGi
Shade
Guide
Time ICC Confidence Interval
Lower Bound Upper Bound
VC Baseline (T1) 0.777 0.674 0.847
1 wk (T2) 0.924 0.889 0.948
1 mo (T3) 0.95 0.868 0.975
3 mo (T4) 0.954 0.93 0.969
BGi Baseline (T1) 0.86 0.645 0.93
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1 mo (T3) 0.984 0.975 0.989
3 mo (T4) 0.982 0.973 0.988
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Table 4: Correlations Between Visual and Instrumental
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Pearson correlation 0.896** 1 0.890**
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DE*
Pearson correlation 0.828** 0.890** 1
p-value 0 0
** Correlation is significant at the 0.01 level, N=360 in all instances.
6Operative Dentistry
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